This has been driving me nuts. I have a CAT 299D2 HXP that the AC was working, then just stopped. The compressor clutch kicks in for less than 2 seconds and kicks out. Here is what i have replaced. *Wiring harness from compressor/relay/pressure stitches to under cab. *All controls on the operator panel. Thermostat / Switch / Fan speed selector. *New relay. They all had some type of damage so i just replaced them. I tested the pressure switches and they tested fine. I checked freon level and its perfect. If i jump across the relay plug, the compressor runs and cools so i swapped the new relay out for another new one and nothing. What am i overlooking?
Have you replaced the accumulator.? If I'm not mistaken it also contains an non-serviceable orifice which tends to block, so if it does you have to replace the whole assembly.
What do the pressure gauges read when the compressor kicks out? I would have to assume it’s only doing what it’s told to do.
With a jumper on the relay plug and compressor running im getting 147 high and 31 on low side. without the jumper, the compressor is only on for a spilt second and the gauges cant respond that fast.
No we have not changed the accumulator. Wouldn't i get funky readings on the gauges if it was blocked?
Have you tried a jumper wire in place of the pressure switch?
Yes i tried jumping them one at a time then both at the same time
Have you jumpered the thermostat switch?
I have not tried it but that's the next thing on my list to check. Been out of commission for a few weeks
So is the thermostat new? Pull the thermostat probe out of the evaporator and see if the compressor stays running.
If system operates, when relay jumped, it sounds like you are missing the ground side of relay, or a 12v input to that relay, Depending on how its wired, most are ground switched, ECM controlled. But it could have continuous ground, ECM switched 12v.
*** SOLVED *** It was the compressor clutch. Swapped the clutch with an aftermarket one and boom! Frosty!